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SCIENCE AND INVENTION, (Concluded) This is ensured by using an achromatic lens satisfying two additional conditions: —the focal distance, on the one hand, is fairly identical with that of the photo
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photograph, a distant image of the latAll metal. Price, $5.00, prepaid in U.S. Send Buy
for FREE descriptive booklet. Agents wanted. ter being free from any deformation (if a Locke
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the eye be placed at the point of no deSave Your Brain.
formation), and fulfilling the same con
ditions as to apparent size, shadows, and THE NEW YEAR'S NUMBER OF relative distinctness as in the case of the
objects being inspected from the objective of the photographic camera. The im
pression thus produced by the small is the largest and the most important number of a photograph will be much more true to power plant paper ever issued. The price of a single copy to non-subscribers, is
nature; and the main consequence will 50 cents. Subscribe now, send us one dollar, and you be an unconscious production of a true will receive the New Year's Number and 23 other numbers during 1905.
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through the apparatus will therefore proThe Engineer Publishing Company duce quite as plastic effects as in the case 357 Dearborn Street :: Chicago, Illinois
of being regarded with both eyes through
a stereoscope.—DR. A. GRADEN WITZ. Mention The Technical World.
Practical Books |
Just Ready-Centrifugal Fans, by J. H. Kinealy.
M. Am. Soc. M. E. Dealing with their designing, construction and use with numerous Formulas, Illustra
Dry Battery-Electro-Gilding Bath tions and Tables. Suitable for archi
Question 1: How can I make a pocket dry tectural and engi
battery? neering drawings.
Question 2: How can I make an electro
gilding bath which gives a red color like 14E SYSTEM 8 NEW
or 18-carat gold?-). V'. C. ALPHABETS.
Answer 1: Dry cells are sold at such a low price that it does not pay an indi
vidual to spend his time in the manufactNinth Thousand.
ure of a cell. A dry battery may be By Mail 50c.
made in the following manner: Care and Handling of Electric Plants.
A jar of the desired shape is made of With very useful table, formulas and suggestions and 66 original drawings.
zinc; heavy sheet zinc should be used In limp leather ... Price $1.00
and bent into the required form, then
soldered in such a manner that it forms Spon & Chamberlain a jar. It will be found difficult to solder Publishers TECHNICAL BOOKS
zinc. All parts where it is desired the T. W., Liberty Building. NEW YORK
solder should stick should be carefully cleaned by scraping, and clean chloride of zinc used as a flux. The zinc should have a brass binding-post soldered to it. The other electrode is usually carbon,
and should have a similar binding-post Twentieth Century
fastened to it.
The contents of such cells vary. In Gassner's cell, the following mixture is
used: ANGUS SINCLAIR COMPANY
Oxide of zinc, 1 part by weight; sal-ammoniac, I part; plaster of paris, 3 parts; chlo
ride of zinc, i part; and water, 2 parts. Newly Published and is the
The cell is sealed by means of covering Best Book on
with pitch, or some similar material Railway Machinery
which will not allow salts to creep. There ever published. Contains
are many other formulæ for the contents chapterson: Elementary
· of the cell, which are used with success. lessons on first principles;
Answer 2: steam and motive power;
The following solution, workshop operations; loco
recommended for red plating, should be motive boiler construction;
used hot (at the boiling point) with a compound locomotives;
platinum wire for the anode and with valve motion; machine tools and shop appliances, and
high current density : on nine other subjects.
Phosphate of soda (crystallized), 60 parts; PROFUSELY ILLUSTRATED.
bisulphite of soda, 10 parts; cyanide of potasContains 670 pages, 6x9 inches.
sium (C. P.), I or 2 parts; neutral chloride PRICE, THREE DOLLARS
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parts. LOCOMOTIVE ENGINEERING
First dissolve the phosphate of soda in
800 parts of hot water. When thoroughly Department T, 136 Liberty Street
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and allow to cool. Dissolve the gold
chloride in 100 parts water, and the biMention The Technical World.
Compendium of Drawing
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900 Pages-1,000 Illustrations, Folding Plates, Etc.
REGULAR price, $10.00, reduced nearly
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LIST OF AUTHORS AND SUBJECTS
Part I PROF. E. KENISON, M. I. T. . . . .
. Mechanical Drawing PROF. H. W. GARDNER, M. I. T.
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..CUT OFF HERE.. American School of Correspondence, Chicago:
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Answer: The pressure at any crosssection of the pipe can be determined by multiplying the head in feet at that section by the factor 433. The greatest pressure on the first 300 feet length of pipe will be that due to the head of 18 feet. This corresponds to a pressure of 7.8 pounds per square inch. The greatest pressure on the last section will be that due to the total head of 55 feet, and is equivalent to 23.8 pounds. By use of the following formula, the necessary thickness of the tube can be de
DXP t = 2X SXE'
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